File Server/Transport/Http/MiddlewarePipeline.php

1:	<?php
2:
3:	declare(strict_types=1);
4:
5:	/**
6:	* This file is part of the Nexus MCP SDK package.
7:	*
8:	* (c) 2026 John Paul E. Balandan, CPA <paulbalandan@gmail.com>
9:	*
10:	* For the full copyright and license information, please view
11:	* the LICENSE file that was distributed with this source code.
12:	*/
13:
14:	namespace Nexus\Mcp\Server\Transport\Http;
15:
16:	use Psr\Http\Message\ResponseInterface;
17:	use Psr\Http\Message\ServerRequestInterface;
18:	use Psr\Http\Server\MiddlewareInterface;
19:	use Psr\Http\Server\RequestHandlerInterface;
20:
21:	/**
22:	* Composes PSR-15 middleware in front of an inner request handler, typically the Streamable HTTP transport.
23:	*
24:	* The middleware run outermost-first. The pipeline is re-entrant: one instance serves concurrent requests,
25:	* since each `handle()` recurses over a fresh immutable tail rather than mutating shared state.
26:	*/
27:	final readonly class MiddlewarePipeline implements RequestHandlerInterface
28:	{
29:	/**
30:	* @var list<MiddlewareInterface>
31:	*/
32:	private array $middleware;
33:
34:	public function __construct(private RequestHandlerInterface $handler, MiddlewareInterface ...$middleware)
35:	{
36:	$this->middleware = array_values($middleware);
37:	}
38:
39:	#[\Override]
40:	public function handle(ServerRequestInterface $request): ResponseInterface
41:	{
42:	if ([] === $this->middleware) {
43:	return $this->handler->handle($request);
44:	}
45:
46:	return $this->middleware[0]->process(
47:	$request,
48:	new self($this->handler, ...\array_slice($this->middleware, 1)),
49:	);
50:	}
51:	}
52:

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